Re: [PATCH][ACPI] AC/DC notifier

From: Pavel Machek
Date: Sat Aug 15 2009 - 12:20:58 EST


On Wed 2009-08-12 01:55:32, Matthew Garrett wrote:
> On Tue, Aug 11, 2009 at 08:51:49PM -0400, Tippett, Matthew wrote:
>
> > From a graphics perspective (your area of expertise), this will allow KMS
> > drivers to do some more intelligent actions based on the ac/dc state.
> > Some examples of this could be improving the power consumption of the
> > graphics hardware through adapting clock memory/engine settings for
> > reduced power consumption, reducing refresh rate of the display to reduce
> > scanout memory access, adjusting backlight brightness, etc.
>
> Right. As you say, my concern is that most of this should belong in
> userspace. Where we risk hardware damage there's an obvious argument for
> doing this in kernel, but we should ensure that that's limited to
> whatever coarse-grain handling is absolutely required rather than doing
> things like touching display brightness.

Yep... Some may want to save power even when AC is online -- like when
running on UPS. Some may want max performmance even on battery.
Pavel

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